A hive whose CA predates the swarm root keeps a self-signed CA, and
nothing re-roots it. That is what makes the hierarchy non-disruptive,
and it also means the O(1)-trust payoff never arrives for that hive.
Adoption now happens by itself where this host owns the root, and
nowhere else. The split is the whole design: adoption invalidates an
anchor consumers already trust, and they refresh on their own schedule —
on one box that schedule is knowable, across hosts it is not. So the
all-local case migrates itself and every other case gets a failure that
names both files, gives the two-command recipe, says why it is not
automatic, and offers the marker as a deliberate opt-out.
The previous CA rides in the trust bundle afterwards. Consumers read the
bundle rather than ca.pem, so adoption is additive before it is
subtractive; agents pick up new trust only when their container
restarts, which is a window even on a single host. Dropping the old
anchor stays a separate, deliberate step.
A swarm's services and its hives can live on different hosts, and a host
has no way to tell whether it is the one holding the root — so setting
the swarm CA up is an operator action, not something a host infers.
`swarm.ca.autoConfigure` is off by default and is the only thing that
issues a hive sub-CA, which is also the only case that *can*: signing
one needs the root's private key, and that key is deliberately not on a
hive host otherwise.
With the flag off, a hive self-signs its CA exactly as it always has.
That keeps a plain hive working out of the box; what it gives up is
membership of a swarm's trust hierarchy, which is the right thing to
give up for a hive nobody has federated.
Replaces a default derived from `swarm.peers == { }`. That read "no
peers declared" as "everything is local", which is not the same claim —
a hive can belong to a swarm it has not declared yet, or to one whose
services run elsewhere entirely.
Cross-hive trust was O(n²) hand-pinning: every hive had to name every
peer's CA. A swarm root makes it O(1) — trust the root once and every
present and future peer validates.
The root is generated by a new `swarm-ca` unit on a single-host swarm
and operator-provided otherwise; `swarm.ca.autoConfigure` picks between
them and derives its default from `swarm.peers` being empty, so "all on
one host" is read off the deployment rather than remembered. Both modes
produce the same artifacts in the same places, so splitting hosts later
is moving the service dirs, not switching code paths. The root key never
enters the nix store, and the root is never regenerated automatically —
replacing it invalidates every peer at once.
Each hive CA carries `nameConstraints` pinned to that hive's domain, so
a leaked hive CA can only mint names inside its own subdomain, enforced
by verifiers rather than by convention.
`ca.pem` was serving as both the issuer and the anchor consumers trust;
those are the same file only while it is self-signed. openssl will not
terminate a chain at a trusted cert that isn't self-signed (rustls and
Go will), so the promotion would have broken some consumers and not
others. `hive-tls-ca` now also writes `trust-bundle.pem` — the hive CA
plus whatever it is rooted at — and every anchor consumer reads that:
agents, the CI and forge containers, and the peer-config recipe. On a
hive with no swarm root the bundle is just that CA, so nothing consuming
it needs a mode to branch on.
